In this proposal I request three years of funding to support a two-fold project. The proposed research has both a substantive and a methodological focus. Substantively, I request support for a component study of cognitive development that will be part of an ongoing longitudinal study of human development using core index cases and spouses from the various Berkeley longitudinal studies of growth and development. Methodologically, I request support for the continued development of analytic procedures for analyzing longitudinal and cohort sequential data. This will be done by the elaboration of specific statistical procedures and by developing relevant computer programs.